Grinding assembly for glass slabs and grinding head for a rectilinear grinding machine equipped with such assembly

ABSTRACT

A grinding assembly is described, for a grinding head for a grinding machine of glass slabs, comprising: a first (and possibly a second) grinding wheel adapted to tangentially work on the glass edge and whose rotation axis A is parallel to the glass edge to be ground; and a handling system for the grinding wheel for adjusting the removal of glass in an oscillating way or in parallel with the plane of the slab to be ground. A grinding head equipped with the above grinding assembly is further described.

CROSS-REFERENCE TO RELATED APPLICATION

The present Application is a national stage of International PatentApplication No. PCT/IT2007/000361, titled “Grinding Assembly for GlassSlabs and Grinding Head for a Rectilinear Grinding Machine Equipped WithSuch Assembly,” filed Sep. 13, 2007, the contents of which areincorporated in this disclosure by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention refers to a grinding assembly for glass slabs andto a grinding head for a rectilinear grinding machine equipped with suchsystem.

2. Background Art

As known, following etching and shearing operations, half-finished glassslabs are obtained, whose perimeter edges are in many cases ground in agrinding plant till the desired final geometry is reached. The grindingplants being used comprise a conveyor adapted to advance the glass slabsalong an horizontal path through one or more working stations, each oneof which houses a plurality of grinding wheels arranged in fixedpositions along the path itself in order to grind two mutually oppositesides of the perimeter edge when advancing each slab.

The products obtained through the above-described known grinding plantshave a not always satisfactory quality index, since, when the glassslabs advance along their related path, positioning and squaring errorsof the slabs with respect to the grinding wheels can occur, so that theground edges outlines sometimes are not perfectly straight or notperfectly orthogonal, with a scarce geometric accuracy of the finishedproduct.

In order to simply and inexpensively solve the above mentioned problem,the Applicant of the present Application has filed patent EP-A-1468784,related to a grinding head 1 (see right side of FIG. 1) that allowsaccurately working each glass slab 2 in a working station where the slab2 itself is kept in a univocal fixed reference position when working itsrelated edge. A plurality of grinding heads 1, like the one disclosed inthe above patent, are adapted to simultaneously work on all sides theglass slabs 2, through workings that are mutually different and are alsooperating at different speeds. The described grinding head 1, as shownin FIG. 1, substantially comprises, arranged in a row along the workingdirection of a glass slab 2: a grinding wheel 20 for the side grindingof the slab 2; a grinding wheel 22 for grinding the upper threads (orbevels) of the slab 2; a grinding wheel 24 for polishing the upperthreads (or bevels) of the slab 2; a grinding wheel 26 for grinding thelower threads (or bevels) of the slab 2; a grinding wheel 28 forpolishing the lower threads (or bevels) of the slab 2; and two grindingwheels 30, 32 for the side polishing of the slab 2. All grinding wheels20 to 32 are supported and rotatingly driven by a respective spindle(not shown), and the grinding wheels 20 to 32 and their respectivespindles are contained in and supported by a supporting structure 9.

It is also known that the removal capacity of a diamond grinding wheelin general essentially depends on its diameter. Therefore, when the head1 must work very thick glass slabs 2, the grinding wheel 20 alone is notadequate for performing such working: it would therefore be necessary toprovide for a grinding wheel 20 with a bigger diameter or an additionalgrinding wheel: both these solutions force to increase the widthencumbrance of the head 1, and this is technically difficult, if notimpossible, to carry out, since the heads 1 that can usually be found ona complete machine are at least four, in a mutual movement one withrespect to the other along the sides of the glass slab 2 to be worked.In the end, the only possible solution with the current art technicalknowledge is greatly increasing the grinding machine sides, whichobviously is not preferable.

SUMMARY OF THE INVENTION

Therefore, object of the present invention is solving the above priorart problems, by providing a grinding head equipped with an innovativegrinding assembly, that allows on one hand to use grinding wheels with avery big diameter (on the order of 200 mm, but that can be adjusted andincreased at will) and on the other hand to only minimally increase thewidth encumbrance of the head, exploiting the thickness, rather than thewidth, of the grinding wheel of which the inventive assembly iscomposed. For this purpose, the grinding wheel of the inventive assemblyworks tangentially on the glass edge, and has it rotation axis parallelto the edge to be ground, differently from all other currently knowngrinding wheels, whose rotation axis is perpendicular or slanted withrespect to the glass edge.

The above and other objects and advantages of the invention, as willappear from the following description, are obtained with a grinding headand machine as disclosed, respectively, in the independent claims.Preferred embodiments and non-trivial variations of the presentinvention are the subject matter of the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better described by some preferredembodiment thereof, provided as a non-limiting example, with referenceto the enclosed drawings, in which:

FIG. 1 is a side view of a preferred embodiment of the grinding headequipped with the grinding assembly according to the present invention;

FIG. 2 is a perspective view of an embodiment of the handling system ofthe grinding assembly of the invention;

FIG. 3 is an exploded perspective view of the handling system of FIG. 2;

FIG. 4 is a schematic view that shows in detail the main operating stepsof the grinding wheel of the grinding assembly of the invention; and

FIG. 5 is a side view of the grinding assembly of FIG. 2 detailing othertwo glass working steps.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the Figures, preferred embodiments of the grindingassembly and head of the present invention are shown and described. Itwill be immediately obvious that numerous variations and modifications(for example related to shape, sizes and parts with equivalentfunctionality) could be made to what is described, without departingfrom the scope of the invention, as appears from the enclosed claims.

With reference to FIG. 1, this has already been previously described,and provides for a grinding head 1, to which a preferred embodiment ofthe grinding assembly 3 of the present invention has been applied. Ascan be well seen from FIG. 1, the inventive assembly 3 is equipped withat least one diamond grinding wheel 5 that tangentially operates on theglass edge 2 and whose rotation axis A is parallel to the edge of theglass 2 to be ground. In this way, the assembly 3 allows saving a lot ofspace in its encumbrance, that is equal to the thickness of the grindingwheel 5, instead of its diameter, that can be thereby equal to 200 mm ormore.

The removal of the grinding wheel 5 is adjusted by moving the grindingwheel 5 itself along the glass 2 direction (as known), through anyhandling system, in an oscillating way (direction B in FIG. 2) or inparallel (direction C in FIG. 2) to the plane of the slab 2 to beworked.

FIGS. 2 and 3 show a preferred, but absolutely not limiting, embodimentof the handling system of the grinding wheel 5, that can be suitablyadapted to the head 1 of FIG. 1. Such system substantially comprises acam-shaped supporting element 11 equipped with pushing means 13(typically a ball re-circulation screw driven by a stepped motor or anyother motor) adapted to push the supporting element 11 in operatingdirections B and C in FIG. 2. Moreover, the system comprises anactuating motor 14 shown in FIG. 3, adapted to transmit the rotarymotion to the grinding wheel 5 through a system with belt 16 and pulleys18, 19.

The particular arrangement of the above mentioned handling system allowshousing the main bearings 40 of the grinding wheel 5 directly inside it(as can be seen in FIG. 3), greatly reducing the projection of thegrinding wheel 5 with respect to a traditional grinding spindle.

It is obvious that the shown handling system is only one of the possiblepractical embodiments in which, from the mechanical point of view,movements of the head 5 can be performed along its two operatingdirections B and C: for example, driving guides could alternatively beprovided, adapted for this purpose.

Still in general terms, the grinding assembly 3 of the present inventioncan be used by moving the grinding wheel 5 along the direction of theedge of the slab 2 to be ground, or by keeping the grinding assemblyfixed and moving the slab 2, for example along the direction designatedwith D in FIG. 1.

As preferred, but not limiting, variation, the grinding wheel 5, ifsuitably shaped at 45°, as can be seen in the drawings, also allowsperforming a bevel on the edge of the glass 2 (operation that is moreand more required by the market due to accident-preventing issues).Traditionally, this operation was performed by an additional grindingwheel, that operated as follower and performed an irregular (rounded)and scarcely accurate bevel.

With the inventive arrangement, instead, on the same hub housing theperipheral grinding wheel 5 of the invention, another grinding wheel 7can be added, that works with the same principle, aimed for exclusivelyperforming the grinding operation of the edge of the glass 2: suchoperation is shown in detail in FIG. 4, where, starting from theposition designated with 1, the grinding wheel 7 is moved next to theangle to be worked with a movement along direction F. As can be seen inposition 2, the grinding wheel 7 obtains a bevel with an operatingadvancement movement along direction E, while afterwards it is quicklymoved away through a movement along direction G, until (position 3) thegrinding wheel 5 is exactly in the correct position to engage the glassslab 2 by advancing along direction F, performing the bevel cutting atthe desired thickness, together with the usual grinding operation of theslab 2.

The grinding wheel 5 of the invention performs, as can be better seen inFIG. 5, a removal of material with a slight curve (Step SB in FIG. 5);such slight curve is afterwards easily removed by the traditionalgrinding wheel 20 for side grinding (Step SA in FIG. 5), therebyefficiently completing the grinding work of the slab 2 with a minimumglobal encumbrance.

Both when it is equipped with the sole grinding wheel 5, and when it isequipped with both grinding wheels 5 and 7, it can therefore be easilyseen that the grinding head 1 of the present invention allows providinga great capacity of removing material from a glass slab 2 of any size,with a really minimum additional encumbrance with respect to traditionalheads.

The thereby shown grinding head 1 allows performing, on a fixed glassslab 2, a plurality of grinding and polishing operations, by driving thegrinding wheels and their related spindles at mutually different speedsand by placing the grinding wheels next to different parts of the slab 2on which it is necessary to perform the relevant working.

1. A grinding assembly for a grinding head for a grinding machine forglass slabs, the grinding assembly comprising: at least one firstgrinding wheel adapted to tangentially work on an edge of the glass slaband whose rotation axis is parallel to the edge of the glass slab to beground; a handling system for the first grinding wheel adapted to movethe first grinding wheel to remove glass from the glass slab throughoscillations or in parallel with the plane of the glass slab to beground; a cam-shaped supporting element equipped with pushing meansadapted to push the supporting element along two operating directions ofthe supporting element; and an actuating motor adapted to transmit arotary motion to the grinding wheel through a system with a belt andpulleys; and the handling system being thereby adapted to house mainbearings of the grinding wheel directly inside the handling system. 2.The grinding assembly of claim 1, wherein the grinding assembly isfurther equipped with at least one second grinding wheel adapted toperform exclusively a grinding operation of an edge of the glass slab,the first grinding wheel being further adapted to cut the edge obtainedby the second grinding wheel at a desired thickness.
 3. The grindingassembly of claim 1, wherein the handling system further comprisesdriving guides.
 4. A method for grinding a slab of glass, the glass slabcomprising an edge, the method comprising: a) providing the grindingassembly of claim 1; and b) moving the grinding wheel along a directionof the edge of the glass slab while keeping the glass slab fixed.
 5. Amethod for grinding a slab of glass, the glass slab comprising an edge,the method comprising: a) providing the grinding assembly of claim 1;and b) keeping the grinding assembly fixed and moving the glass slab. 6.The grinding assembly of claim 1, wherein the grinding wheel comprises aworking surface shaped at 45° in order to perform a bevel on the edge ofthe glass slab.
 7. A grinding head for a grinding machine for glassslabs comprising: a supporting structure; at least one first grindingwheel for laterally grinding the glass slabs, the first grinding wheelbeing supported and rotatingly driven by a first spindle, the firstgrinding wheel and the first spindle being contained in and supported bythe supporting structure; at least one second grinding wheel forgrinding upper threads of the glass slabs, the second grinding wheelbeing supported and rotatingly driven by a second spindle, the secondgrinding wheel and the second spindle being contained in and supportedby the supporting structure; at least one third grinding wheel forpolishing the upper threads of the glass slabs, the third grinding wheelbeing supported and rotatingly driven by a third spindle, the thirdgrinding wheel and the third spindle being contained in and supported bythe supporting structure; at least one fourth grinding wheel forgrinding lower threads of the glass slabs, the fourth grinding wheelbeing supported and rotatingly driven by a fourth spindle, the fourthgrinding wheel and the fourth spindle being contained in and supportedby the supporting structure; at least one fifth grinding wheel forpolishing lower threads of the glass slabs, the fifth grinding wheelbeing supported and rotatingly driven by a fifth spindle, the fifthgrinding wheel and the fifth spindle being contained in and supported bythe supporting structure; and at least one sixth grinding wheel forlaterally polishing the glass slabs, the sixth grinding wheel beingsupported and rotatingly driven by a sixth spindle, the sixth grindingwheel and the sixth spindle being contained in and supported by thesupporting structure; the first grinding wheel and the sixth grindingwheel rotating, in a mutually independent way, around an axis that isperpendicular to an edge of the glass slabs, the second, third, fourthand fifth grinding wheels rotating, in a mutually independent way,around an axis that is slanted with respect to the edge of the glassslabs, the second, third, fourth and fifth grinding wheels being adaptedto perform, when working, an axial movement along the glass slabs, theaxial movements of the second, third, fourth and fifth grinding wheelsbeing adapted to be activated independently one from the other, whereinthe grinding head further comprises at least one grinding assembly. 8.The grinding head of claim 7, wherein the at least one sixth grindingwheels are two and are rotatingly driven by two respective sixthspindles.